Which clams have pearls

In freshwater cultured pearls, cutting the mantle is enough to induce the nacre secretion that produces a pearl -- an irritant doesn't have to be inserted. While cultured and natural pearls are considered to be of equal quality, cultured pearls are generally less expensive because they aren't as rare.

Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Wild Animals. Marine Life. How Do Oysters Make Pearls? Updated: Apr 16, Oysters aren't the only type of mollusk that can produce pearls; clams and mussels can as well. Tel: Email: info centreofthecell. Necessary cookies are absolutely essential for the website to function properly.

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Book Contact us. By Myfi Williams Pearls are seen as objects of beauty; we have used them for jewellery and decoration for hundreds of years. A macrophage. Support us Find out more. Receive our newsletter. As the oyster recognises the nucleus as an irritant, it forms a sac around the irritant before coating it with smooth layers of nacre.

Pearl farms now produce all the cultured pearls used in the jewellery industry today, and, while they are real, genuine pearls formed inside a living oyster, they are produced with a little human intervention.

Saltwater oysters are nucleated by opening the shell a mere 2 to 3 centimetres and making a minute incision in the gonad - the oyster's reproductive organ. The mother of pearl nucleus is inserted into this incision which is then followed with a very small piece of mantle tissue from a donor oyster. The mantle tissue is placed between the mother of pearl bead and the gonad with the side containing epithelial cells facing the nucleus.

These epithelial cells are the catalyst of the pearl-sac. The pearl sac grows around the nucleus and begins to deposit nacre. This nacre layering is the beauty of the pearl. Saltwater oysters will only produce 1 to 2 pearls per typical nucleation.

Akoya oysters can be nucleated with up to 5 beads but the use of only 2 is most common. The Akoya oyster dies at harvest. South Seaoysters Pinctada margaritifera and Pinctada maxima accept only one nucleus at a time but, as they do not die at harvest, they may be nucleated several times.

If a particular oyster has been successfully nucleated several times and consistently produces fine pearls, the oyster is often returned to the wild to strengthen the genes of future generations of spat. An oyster's pearl sac will secrete nacre on nearly any solid object. This has led to countless attempts to nucleate oysters with material other than oyster shell.

Success has been limited, however, and oyster shell is still the main staple of the pearl farmer as it has been since the early s. The reasons nuclei of non-standard composition has been so quickly rejected in the past is because the density of the nucleus must exactly match, or be extremely close to the density of the host mussel.

In order for the pearl to expand and contract in different environments, the nucleus must expand and contract in a compatible fashion. This is known as the thermal coefficient of expansion. The nuclei must also resist cracking, hold a high shine and remain stable over long periods of time. The material that best fits these criteria is the shell of the Mississippi freshwater mussel from the Unionidae family. This mussel has the added attribute of a thick shell, especially in the joint where the bivalve connects.

This thick shell enables harvesters to create large nuclei to be used in culturing larger pearls. The nucleus of a pearl, although it is not typically visible in a harvested pearl, is extremely important in the culturing process.

The nucleus is the seed that impregnates the oyster and produces the gem, although the process is not complete unless a small piece of mantle tissue is inserted with the bead. Cite this Article Format. Kennedy, Jennifer. Mollusk Facts: Habitat, Behavior, Diet. What Is a Mantle in the Body of a Mollusk? Scallop Facts: Habitat, Behavior, Diet. Midden: An Archaeological Garbage Dump. Nautilus Facts: Habitat, Behavior, Diet. Animals of Australia's Great Barrier Reef. Your Privacy Rights.

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